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Transcript

Hi.My name is Uri Alon from the
Weizmann Institute in Israel.Today I'm going to talk with you
about evolutionary trade-offsand the geometry of
gene expression space.

0:11

The basic idea is that when you
have trade-offs between tasks,they lead to simplicity,
a simple geometryof the phenotypes in trait space.

0:23

Now, when we think about
evolution and evolutionary theory,we usually think
about a simple picturewhere the DNA, the genotype,
through developmental processesgives rise to the organism's
shape, the phenotype.And the phenotype does
something to give you fitness.For example, the bird's
beak eats the seeds.The better it eats
the seeds, the morefit the organism, the more
viable babies that it makes.

0:49

And conceptually,
we can describe thisin terms of a fitness landscape.So we think about things we
can measure about the beak.We take a ruler, and
we measure its heightand its width and its lengths.And each trait like that is an
axis, and so we have the trait spacedescribes all possible beak shapes.And for each point in that space,
we can imagine the fitness of a birdwith that beak.And if we can imagine
a fitness landscape,it might have a peak
or several peaks.And natural selection tends to
maximize fitness and bring youto the maximum of the
fitness landscape.